Reference Signal Design for Wireless Communication Systems

ABSTRACT

Systems, methods, and instrumentalities are disclosed for phase noise reference signal (PNRS) transmission, comprising receiving, at a wireless transmit receive unit (WTRU), scheduling information for a Physical Uplink Shared Channel (PUSCH) transmission, wherein the scheduling information includes an indication of a set of physical resource blocks (PRBs) and a modulation coding scheme (MCS) level, determining a density for the PNRS transmission based on at least one of: the MCS level, a frequency band for the PUSCH transmission, or a subcarrier spacing of the PUSCH transmission, and transmitting the PUSCH in the scheduled set of PRBs using the determined density of PNRS.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 17/902,098, filed Sep. 2, 2022, which is a continuation of U.S.U.S. Non-Provisional application Ser. No. 16/337,774, filed Mar. 28,2019, which issued as U.S. Pat. No. 11,477,813 on Oct. 18, 2022, whichis the National Stage entry under 35 U.S.C. § 371 of Patent CooperationTreaty Application PCT/US2017/053980, filed Sep. 28, 2017, which claimspriority to, and the benefit of, U.S. Provisional Application Ser. No.62/400,925, filed Sep. 28, 2016, U.S. Provisional Application Ser. No.62/454,617, filed Feb. 3, 2017, U.S. Provisional Application Ser. No.62/519,424, filed Jun. 14, 2017, and U.S. Provisional Application Ser.No. 62/556,146, filed Sep. 8, 2017, which are hereby incorporated byreference herein as if reproduced in their entireties.

BACKGROUND

3GPP is working on an advanced wireless communication system, which maybe referred to as New Radio (NR). Applications of NR may be summarizedunder certain categories which may include one or more of the following:Enhanced mobile broadband (eMBB), Massive machine-type communications(mMTC), or and Ultra-reliable-and-low-latency communications (URLLC).Under a category, there may be a wide set of applications that areconsidered for various needs and deployment scenarios that may mandatespecific performance requirements. For example, mMTC and URLLCapplications may range from automotive to health, agriculture,utilities, and logistics industries.

For mMTC applications, it is expected that the system may be able tosupport up to 1 Million mMTC devices per Km² with extended coverage, lowpower consumption, and/or low device complexity. To support highconnection density, non-orthogonal multiple access techniques may beproposed for NR. For URLLC applications, the WTRU density per cell maybe (e.g., significantly) less. A target delay of <1 ms and/or a highreliability of 10-5 bit error rate may be targets for URLLC.

SUMMARY

Systems, methods, and instrumentalities are disclosed for phase noisereference signal (PNRS) transmission, comprising receiving, at awireless transmit receive unit (WTRU), scheduling information for aPhysical Uplink Shared Channel (PUSCH) transmission, wherein thescheduling information includes an indication of a set of physicalresource blocks (PRBs) and a modulation coding scheme (MCS) level,determining a density for the PNRS transmission based on at least oneof: the MCS level, a frequency band for the PUSCH transmission, or asubcarrier spacing of the PUSCH transmission, and transmitting the PUSCHin the scheduled set of PRBs using the determined density of PNRS.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings.

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A.

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A.

FIG. 2 illustrates an example of PNRS using a same subcarrier locationover consecutive OFDM symbols.

FIG. 3 illustrates an example of PNRS with unused adjacent subcarriers.

FIG. 4 illustrates an example of a lower density PNRS pattern.

FIG. 5 illustrates an example of pre-DFT PNRS insertion via puncturing.

FIG. 6 illustrates an example of pre-DFT PNRS insertion viamultiplexing.

FIG. 7 illustrates an example of pre-DFT PNRS insertion viamultiplexing.

FIG. 8 illustrates an example base PTRS pattern with cyclic shift (CS)values.

FIG. 9 illustrates example WTRU-specific zero-power and non-zero-powerPTRS patterns with different CS values.

FIG. 10 illustrates example WTRU-specific OCC for PTRS tones within aPTRS chunk.

FIG. 11 illustrates an example of Post-DFT PNRS insertion viapuncturing.

FIG. 12 illustrates an example of post-DFT PNRS insertion viamultiplexing.

FIG. 13 illustrates an example of Post-DFT PNRS insertion viamultiplexing.

FIG. 14 illustrates an example puncturing in OFDM for PNRS insertion.

FIG. 15 illustrates an example of PNRS and EPDCCH resource setassociation.

FIG. 16 illustrates an example of PNRS and PRB set association.

FIG. 17 illustrates an example of distributed DM-RS mapped to thecontrol/data part of the sub-frame.

FIG. 18 illustrates an example of a WTRU transmitting the same SRS whilethe eNB is sweeping its receive beam.

FIG. 19 illustrates an example of the WTRU sweeping its SRS.

FIG. 20 illustrates an example of SRS transmission for beam measurement.

FIG. 21 illustrates an example of SRS transmission with subband hopping.

FIG. 22 illustrates an example of SRS transmission and RE muting.

FIG. 23 illustrates an example of port multiplexing using IFDMA withorthogonal sequences and repetition.

FIG. 24 illustrates an example of FDM of DM-RS symbols without timedomain cover codes.

FIG. 25 illustrates an example of FDM of DM-RS symbols with time domaincover codes.

FIGS. 26 and 26A illustrate an example of PNRS frequency density.

FIG. 27 illustrates an example of determining a frequency density for aPNRS transmission.

DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN104/113, a CN 106/115, a public switched telephone network (PSTN) 108,the Internet 110, and other networks 112, though it will be appreciatedthat the disclosed embodiments contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d may be any type of device configured to operateand/or communicate in a wireless environment. By way of example, theWTRUs 102 a, 102 b, 102 c, 102 d, any of which may be referred to as a“station” and/or a “STA”, may be configured to transmit and/or receivewireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (I) device, a watch orother wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106/115, the Internet110, and/or the other networks 112. By way of example, the base stations114 a, 114 b may be a base transceiver station (BTS), a Node-B, an eNodeB, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller,an access point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104/113, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals on one or morecarrier frequencies, which may be referred to as a cell (not shown).These frequencies may be in licensed spectrum, unlicensed spectrum, or acombination of licensed and unlicensed spectrum. A cell may providecoverage for a wireless service to a specific geographical area that maybe relatively fixed or that may change over time. The cell may furtherbe divided into cell sectors. For example, the cell associated with thebase station 114 a may be divided into three sectors. Thus, in oneembodiment, the base station 114 a may include three transceivers, i.e.,one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and mayutilize multiple transceivers for each sector of the cell. For example,beamforming may be used to transmit and/or receive signals in desiredspatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104/113 and the WTRUs 102 a,102 b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 115/116/117 using wideband CDMA (WCDMA).WCDMA may include communication protocols such as High-Speed PacketAccess (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-SpeedDownlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., a eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106/115.

The RAN 104/113 may be in communication with the CN 106/115, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. The data may have varying qualityof service (QoS) requirements, such as differing throughputrequirements, latency requirements, error tolerance requirements,reliability requirements, data throughput requirements, mobilityrequirements, and the like. The CN 106/115 may provide call control,billing services, mobile location-based services, pre-paid calling,Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication. Although notshown in FIG. 1A, it will be appreciated that the RAN 104/113 and/or theCN 106/115 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 104/113 or a different RAT. Forexample, in addition to being connected to the RAN 104/113, which may beutilizing a NR radio technology, the CN 106/115 may also be incommunication with another RAN (not shown) employing a GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106/115 may also serve as a gateway for the WTRUs 102 a, 102 b,102 c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104/113 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) anddownlink (e.g., for reception) may be concurrent and/or simultaneous.The full duplex radio may include an interference management unit toreduce and or substantially eliminate self-interference via eitherhardware (e.g., a choke) or signal processing via a processor (e.g., aseparate processor (not shown) or via processor 118). In an embodiment,the WRTU 102 may include a half-duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for either the UL (e.g., for transmission) or thedownlink (e.g., for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (or PGW) 166. While each of the foregoing elements are depictedas part of the CN 106, it will be appreciated that any of these elementsmay be owned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In certain representative embodiments, the DLS may use an 802.11e DLS oran 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS)mode may not have an AP, and the STAs (e.g., all of the STAs) within orusing the IBSS may communicate directly with each other. The IBSS modeof communication may sometimes be referred to herein as an “ad-hoc” modeof communication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In certainrepresentative embodiments, Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA) may be implemented, for example in in 802.11systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed/detectedand/or determined to be busy by a particular STA, the particular STA mayback off. One STA (e.g., only one station) may transmit at any giventime in a given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications, such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 113 and the CN 115according to an embodiment. As noted above, the RAN 113 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 113 may also be in communication with theCN 115.

The RAN 113 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 113 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containingvarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, dual connectivity, interworkingbetween NR and E-UTRA, routing of user plane data towards User PlaneFunction (UPF) 184 a, 184 b, routing of control plane informationtowards Access and Mobility Management Function (AMF) 182 a, 182 b andthe like. As shown in FIG. 1D, the gNBs 180 a, 180 b, 180 c maycommunicate with one another over an Xn interface.

The CN 115 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whileeach of the foregoing elements are depicted as part of the CN 115, itwill be appreciated that any of these elements may be owned and/oroperated by an entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different PDU sessions with differentrequirements), selecting a particular SMF 183 a, 183 b, management ofthe registration area, termination of NAS signaling, mobilitymanagement, and the like. Network slicing may be used by the AMF 182 a,182 b in order to customize CN support for WTRUs 102 a, 102 b, 102 cbased on the types of services being utilized WTRUs 102 a, 102 b, 102 c.For example, different network slices may be established for differentuse cases such as services relying on ultra-reliable low latency (URLLC)access, services relying on enhanced massive mobile broadband (eMBB)access, services for machine type communication (MTC) access, and/or thelike. The AMF 162 may provide a control plane function for switchingbetween the RAN 113 and other RANs (not shown) that employ other radiotechnologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP accesstechnologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN115 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 115 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating WTRU IPaddress, managing PDU sessions, controlling policy enforcement and QoS,providing downlink data notifications, and the like. A PDU session typemay be IP-based, non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering downlink packets, providing mobility anchoring, and thelike.

The CN 115 may facilitate communications with other networks. Forexample, the CN 115 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 115 and the PSTN 108. In addition, the CN 115may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a localData Network (DN) 185 a, 185 b through the UPF 184 a, 184 b via the N3interface to the UPF 184 a, 184 b and an N6 interface between the UPF184 a, 184 b and the DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

In LTE as an example, orthogonal frequency division multiplexing (OFDM)may be used for downlink (DL) transmission and/ordiscrete-Fourier-transform spread OFDM (DFT-s-OFDM) may be used foruplink (UL) transmission. In Cyclic Prefix (CP) DFT-s-OFDM (sometimesreferred to as single carrier (SC) SC-FDMA with multiple accessing), thedata symbols may be first spread with a DFT block, and then mapped tothe corresponding inputs of an IDFT block. The CP may be prepended tothe beginning of the symbol in order to avoid inter-symbol interference(ISI) and allow one-tap frequency domain equalization (FDE) at thereceiver.

In downlink transmission, reference symbols may be scattered overspecific subcarriers, e.g., one OFDM symbol has subcarriers loaded withdata and reference symbols. Common reference symbols may be transmittedon subcarriers distributed over the system bandwidth and/orWTRU-specific reference signals may be distributed over the subband thatis allocated to a specific WTRU.

For the next generation of wireless communication systems, referencesignal design may be needed to address phase noise problems that mayoccur when operating in the high frequency bands. For high mobilityscenarios, enhancements of RS design may be needed, e.g., to estimateand compensate the Doppler shift. It may be desirable to have a commonuplink/downlink/sidelink RS design, with low overhead.

Systems, methods, and instrumentalities are disclosed, for example, totransmit a DL signal from multiple TRPs with phase noise referencesignal (PNRS). PNRS design/configuration, use of PNRS with multipleTRPs, and PNRS for UL transmission are disclosed.

Assuming x is the OFDM symbol after the IFFT (e.g., without CP), θ_(t)is the transmitter phase noise vector, the received signal after CPremoval may be written as r={x⊙θ_(t)}

h.

After the DFT operation at the receiver, v={d

Θ_(t)}⊙H, where Θ_(t)=Fθ_(t) and =Fh. This means the data vector may becircularly convolved with the phase noise spectrum and the result may bescaled by the channel response. Depending on the spectrum of the phasenoise, data symbol per subcarrier may be rotated with a common phaseerror and contaminated by inter-carrier interference. The PSD of thephase noise may be fast decaying, and, the ICI contribution may bemostly from the adjacent subcarriers. If there is a receiver phasenoise, then v=Θ_(r)

{{d

Θ_(t)}⊙H} where Θ_(r) is the spectrum of the receiver phase noise.

A reference signal may be used to compensate the phase noise and thereference signal may be transmitted over consecutive OFDM symbols in asubframe (or TTI), this may accurately estimate time-variant phasenoise. One or more of following may apply: a reference signal used tocompensate the phase noise may be referred to as phase noise referencesignal (PNRS) (the PNRS may, for example, be interchangeably used withphase tracking reference signal (PTRS), phase noise compensationreference signal (PNCRS), and phase error tracking reference signal(PETRS)); the phase noise reference signal may be used to estimate phasenoise, and, it may be used for other purposes including one or more oftime and/or frequency offset tracking, synchronization, measurement(e.g., RSRP), CSI estimation (e.g., CQI, PMI), or demodulation of adownlink signal; or the PNRS may be transmitted in one or moresubcarriers in an OFDM symbol and the same subcarriers may be used inconsecutive OFDM symbols within a time window (e.g., see FIGS. 2 and 3as examples).

In a case where the PNRS is transmitted in one or more subcarriers in anOFDM symbol and the same subcarriers may be used in consecutive OFDMsymbols within a time window, one or more of the following may apply.The one or more subcarrier indices which may be used for PNRStransmission may be determined based on at least one system parameter(e.g., physical cell-ID, virtual cell-ID, TRP ID, subframe number,and/or radio frame number), and, PNRS collision between neighboringcells may be avoided. The one or more time/frequency resources for PNRSwhich may be associated with another cell or TRP may be muted, reserved,or unused for downlink signal transmission. A subband (e.g., 12subcarriers) may be reserved for a PNRS transmission and at least onesubcarrier in the subband may be selected, determined, or used for aPNRS transmission based on at least one system parameter. The subbandmay not be used for other downlink signal transmissions (e.g., control,data, and/or broadcasting). The one or more subcarrier indices which maybe used for PNRS transmission may be predefined. For example, a centersubcarrier in a system bandwidth may be used for PNRS transmission. Thenumber of subcarriers used for PNRS transmission may be indicated from abroadcasting signal. The one or more subcarrier indices may be thesubcarrier index within a PRB which may be one of the scheduled PRBs andcarry PNRS.

FIG. 2 illustrates an example of PNRS using a same subcarrier locationover consecutive OFDM symbols. FIG. 3 illustrates an example of PNRSwith unused adjacent subcarriers.

The lower density of the PNRS patterns may be defined. These lowerdensity PNRS patterns may be configured by the eNB, for example if thecorrelation time of the phase noise is larger than the OFDM symbollength. An example of a lower density PNRS pattern is shown in FIG. 4 .A density of PNRS may be determined based on the density in time domain(e.g., the number of OFDM symbols containing PNRS within a time window(e.g., slot, subframe, TTI) and/or the density in frequency domain(e.g., the number of subcarriers used for PNRS within a systembandwidth, a PRB, a PRB-pair, or a scheduled bandwidth)). FIG. 3 showsan example of PNRS with a high density (e.g., in time domain). FIG. 4shows an example of PNRS with a low density (e.g., in time domain),wherein the lower density PNRS may use a subset of PNRS transmitted orused for higher density PNRS.

The PNRS may be configured for a lower or higher density pattern, e.g.,as a function of the numerology (e.g., the sub-carrier spacing and theOFDM symbol duration). For example, for a system operating with a shortOFDM symbol duration, a lower density PNRS pattern may be used, e.g.,when the correlation time of the phase noise is larger than the OFDMsymbol duration. The PNRS density (or density pattern) can be determinedbased on one or more of the following: subcarrier spacing used orconfigured for a unicast traffic (e.g., PDSCH, PUSCH); scheduledbandwidth; TTI length; presence of additional DM-RS; resource allocationtype; or number of layers.

Subcarrier spacing may be used or configured for a unicast traffic(e.g., PDSCH, PUSCH). A set of subcarrier spacing may be used for aunicast traffic and one of the subcarrier spacings may be configured orused for a PDSCH or a PUSCH transmission, e.g., the PNRS density may bedetermined based on the subcarrier spacing used or configured. Forexample, the set of subcarrier spacing {15, 30, 60, 120, 240}kHz may beused and if a WTRU is configured with a subcarrier spacing {15}kHz, theno PNRS may be transmitted (e.g., zero PNRS density), and if the WTRU isconfigured with a subcarrier spacing {240}kHz, a PNRS with a highdensity may be used. A set of PNRS densities may be used and a subset ofPNRS densities may be determined based on a subcarrier spacing used. OnePNRS density within the subset may be determined based on otherscheduling parameter(s) (e.g., modulation order, MCS level, schedulingbandwidth, number of layers, etc.). For example, Nd PNRS densities maybe used as {PNRS-1, PNRS-2, . . . , PNRS-Nd} and each subcarrier spacingmay be associated with a subset of PNRS densities. For example, thefirst subcarrier spacing (e.g., 15 kHz) may be associated with thesubset of PNRS densities {PNRS-1} and the second subcarrier spacing(e.g., 30 kHz) may be associated the subset of PNRS densities {PNRS-1,PNRS-2}; the third subcarrier spacing (e.g., 240 kHz) may be associatedwith the subset of PNRS densities {PNRS-Nd-1, PNRS-Nd} etc. The PNRSdensity subset may be determined based on the subcarrier spacingdetermined. Within the subset of PNRS densities, one PNRS density may bedetermined for PDSCH or PUSCH transmission, e.g., based on one or moreof scheduling parameters. The PNRS-1 may be zero PNRS density, which hasno PNRS within the scheduled bandwidth.

The PNRS densities may be determined based on the scheduled bandwidthfor PDSCH or PUSCH. For example, the number of subcarriers used for PNRSwithin a scheduled bandwidth may be determined based on the number ofPRBs or PRB-pairs allocated within the scheduled bandwidth. One or moresubcarrier per scheduled PRBs may be used for PNRS transmission orreception, e.g., when the number of PRBs scheduled is smaller than afirst threshold. A subset of PRBs within a scheduled resources may beused for PNRS transmission or reception if the number of PRBs scheduledis equal to or larger than a first threshold. A subset of PNRS densitiesmay be determined based on a subcarrier spacing and a PNRS densitywithin the subset of PNRS densities may be determined based on thenumber PRBs scheduled (e.g., scheduled bandwidth). The scheduledbandwidth may be interchangeably used with the number of PRBs scheduled.

The PNRS frequency density may be determined based on the TTI length.The TTI length may be the number of OFDM or DFT-s-OFDM symbols used fora PDSCH or PUSCH transmission or reception, wherein a default TTI lengthmay be defined as a slot (e.g., 14 OFDM symbols for a slot) and ashorter TTI length may be defined as a mini-slot (e.g., the number ofOFDM symbols for a mini-slot may be from 1 to 7 OFDM symbols). Forexample, the PNRS time density may be determined based on the TTIlength. A higher frequency density of PNRS may be used for a shorter TTIlength. A lower frequency density of PNRS may be used for a longer TTIlength.

DM-RS density may be determined based on the presence of additionalDM-RS, where the additional DM-RS may be transmitted when configuredand/or determined based on one or more of scheduling parameters. When anadditional DM-RS is present, a lower density PNRS may be used, where thelower density PNRS may include no PNRS (e.g., zero PNRS density). Thedefault DM-RS may be located within a first part of a slot (e.g., thefirst 1 or 2 OFDM symbols within a slot) which may be referred to as afront-loaded DM-RS and an additional DM-RS may be located in a laterpart of the slot (e.g., at the end of OFDM symbols within a downlinkpart of the slot).

A first PNRS density may be used for a first resource allocation type(e.g., contiguous frequency resource allocation) and a second PNRSdensity may be used for a second resource allocation type (e.g.,non-contiguous frequency resource allocation).

The PNRS density may be determined based on the number of layers used,wherein the layer may be a data stream and the number of layer may beinterchangeably used with the transmission rank. A higher density may beused for a higher number of layers and a lower density may be used for alower number of layers.

The PNRS may be inserted as an input to the IFFT block (e.g., when OFDMis used for transmission) and it may be transmitted on a reservedsubcarrier, e.g., as illustrated in FIG. 2 and FIG. 3 . In FIG. 3 , thesubcarriers adjacent to the PNRS are left blank, which may minimize theinterference on the PNRS. The PNRS may be inserted as an input to theDFT block together with the data symbols (e.g., when DFT-s-OFDM is usedfor transmission). PNRS may be inserted in time domain, after the IFFT,e.g., by puncturing some of the time-domain samples and replacing themwith pilot symbols. The adjacent subcarriers (e.g., a subcarrier next tothe subcarrier containing PNRS) may be blank, unused, and/or muted. AWTRU may be scheduled in a subband which may include PNRS and adjacentsubcarriers. The WTRU may assume that the adjacent subcarriers aremuted, and, the WTRU may rate-match around or puncture the adjacentsubcarriers for its scheduled downlink transmission.

Puncturing and or multiplexing the PNRS may be provided. In thefollowing, phase noise reference signal (PNRS) and phase trackingreference signal (PTRS) may be used interchangeably.

Pre-DFT PTRS may be provided. The phase noise reference signals may beinserted into the DFT block in a system transmitting using theDFT-s-OFDM waveform. One or more of the following may apply (e.g.,features relating to those illustrated in FIG. 5 and FIG. 6 ).

In examples, puncturing may be provided. FIG. 5 illustrates an exampleof pre-DFT PNRS insertion via puncturing. The number of the data symbolsmay match the number of the inputs of the DFT. Some of these datasymbols may be punctured and/or replaced with reference symbols, e.g.,before they are mapped to the corresponding inputs of the DFT block. Asan example, assume one subframe has 14 OFDM symbols and 24 subcarriersare allocated for data transmission; so the size of the DFT is set to24. If QPSK is used, 24×14=336 QPSK symbols may be transmitted in asubframe. With 1/2 coding rate, this may correspond to 336 informationbits. If 4 reference symbols are transmitted per OFDM symbol, then 20QPSK symbols (e.g., only 20 QPSK symbols) can be mapped to the DFTblock. The remaining 4 QPSK symbols may be replaced by the referencesymbols.

In examples multiplexing may be provided. FIG. 6 illustrates an exampleof pre-DFT PNRS insertion via multiplexing. The number of data symbolsto be transmitted in an OFDM symbol may be smaller than the DFT size.After the data symbols are mapped to the corresponding inputs of theDFT, it may still be possible to insert additional symbols into the DFTblock. These additional symbols may be selected to be reference symbols.Using the same example above, with multiplexing, the number ofinformation bits transmitted in the subframe may be 280 bits. After 1/2rate coding and QPSK modulation, each OFDM block may transmit 20 QPSKsymbols. The remaining 4 inputs of the DFT block may be used by thePNRS, e.g., since the DFT size is 24.

The density of PNRS in DFT-s-OFDM using pre-DFT PNRS insertion may bedetermined based on number of DFT-s-OFDM symbols containing PTRS, whichmay be referred to as PNRS time density and number of symbols within thedata symbols (or data symbol vector) for a DFT input which may bereferred to as a PNRS frequency density. The PNRS density may bedetermined based on one or more of DFT size or a number of DFT blocks.For example, the DFT size of DFT-s-OFDM for PUSCH transmission may beused to determine the PNRS frequency density (e.g., number of symbolsused for PNRS within the data symbol vector). One or more DFT blocks maybe used for PUSCH transmission and the PNRS density may be determinedbased of the number of DFT blocks. A higher PNRS density may be usedwhen the number of DFT blocks is larger than one, while a lower PNRSdensity may be used when the number of DFT block is one. The number ofDFT blocks may be larger than one when the scheduled uplink resource isnot contiguous in frequency domain.

Chunk-based pre-DFT PTRS insertion may be performed. A PTRS pattern fora chunk-based pre-DFT PTRS insertion may be determined based on at leastone of a number of PTRS chunks (Nc), a chunk size (Ns), or locations ofNc chunks within the DFT inputs (or DFT input signal). FIG. 7 shows anexample of a PTRS pattern with Nc and Ns values of a PTRS pattern,wherein Nc=N chunks with Ns=3 are used. The chunk size (Ns) may be thenumber of PTRS tone(s) within a chunk. The PTRS tone may beinterchangeably used with PTRS sample, PTRS RE, and/or PTRS subcarrier.

A group of PTRS patterns that may have the same density may be referredto as a PTRS type. PTRS patterns in a same PTRS type may have differentNs and/or Nc values while the total number of PTRS tones (e.g., Ns×Nc)is the same. The total number of PTRS tones may be interchangeably usedwith PTRS density.

In examples, a first PTRS type (e.g., PTRS Type-1) may be based on thePTRS density=4. A first PTRS pattern in the PTRS Type-1 may be Nc=2 andNs=2, and a second PTRS pattern in the PTRS Type-1 may be Nc=4 and Ns=1.

In examples, a first PTRS type (e.g., PTRS Type-1) may be based on thePTRS density=4. The PTRS patterns in the PTRS Type-1 may have the sameNc and Ns values while the locations of Nc chunks may be different. Forexample, when Nc=2, a first PTRS pattern may have the PTRS chunks at thefront and the end of the DFT inputs. A second PTRS pattern may have thePTRS chunks at the middle and the end of DFT inputs. A third PTRSpattern may have the PTRS chunks at the front and the middle.

The locations of Nc chunks in a DFT input may be determined based on acyclic shift value of DFT input signal and/or IDFT output signal. A basePTRS pattern may be defined, determined, or configured and its cyclicshift versions may be considered as or referred to as different PTRSpatterns in a same PTRS type. For example, a base PTRS pattern may bereferred to as a PTRS pattern with zero cyclic shift value (e.g., CS=0),a cyclic shifted version of the base PTRS pattern may be referred to asa PTRS pattern with a cyclic shift value (e.g., CS=1). A cyclic shiftedversion of the base PTRS pattern may be referred to as a PTRS pattern inthe same PTRS type.

The PTRS density may be different based on the PTRS pattern and/or PTRStype. For example, a first PTRS pattern (or PTRS type) may have a firstPTRS density and a second PTRS pattern (or PTRS type) may have a secondPTRS density, wherein the first PTRS density may be higher than thesecond PTRS density. The PTRS density may be referred to as the numberof PTRS tones for the DFT inputs and/or the number of DFT-s-OFDM symbolscontaining PTRS in a PUSCH transmission. The PTRS density may bereferred to as the number of PTRS subcarriers within a scheduledbandwidth and/or the number of OFDM symbols containing PTRS in a PUSCHor PDSCH. A PTRS density (e.g., in frequency domain may be referred toas a PTRS subcarrier) is used every Np scheduled PRBs, wherein thestarting PRB may be determined based on at least one of a fixed number(e.g., a first PRB of the scheduled PRBs), a configured number (e.g., ahigher layer configured parameter), a number determined based on aWTRU-specific parameter (e.g., WTRU-ID, scrambling ID), and a cellspecific parameter (e.g., cell-ID). The allocated PRBs may be orderedfrom 0 to Nprb−1 irrespective of the PRB locations, wherein Nprb may bereferred to as the number of PRBs allocated for the WTRU.

A PTRS density, a PTRS pattern, a chunk size of a PTRS pattern, a numberof chunks of a PTRS pattern, and/or a PTRS type for a PUSCH transmissionmay be determined based on at least one of a scheduled bandwidth,modulation order or modulation and coding scheme (MCS) level,numerology, transport block size (TBS) and/or DM-RS configuration forthe scheduled PUSCH transmission. Numerology may include at least one ofa subcarrier spacing, a slot length, a TTI length, and a CP length.

In examples, a first PTRS pattern may be used if a scheduled bandwidthfor a PUSCH transmission is less than or equal to a first threshold, anda second PTRS pattern may be used if a scheduled bandwidth for a PUSCHtransmission is greater than the first threshold and less than or equalto a second threshold. The scheduled bandwidth may be interchangeablyused with DFT input size.

In examples, a first PTRS pattern may be used if a scheduled modulationorder or MCS level is less than or equal to a first threshold, and asecond PTRS pattern may be used if a scheduled modulation order or MCSlevel is greater than the first threshold and less than or equal to asecond threshold.

A DM-RS configuration may be based on the number of DM-RS symbols (e.g.,DFT-s-OFDM symbols or CP-OFDM symbols used for DM-RS transmission)and/or the location of DM-RS symbols. For example, a first DM-RSconfiguration may have two DM-RS symbols that may be located at thefirst two DFT-s-OFDM symbols or CP-OFDM symbols, and a second DM-RSconfiguration may have two DM-RS symbols that may be located at thefirst DFT-s-OFDM symbol or CP-OFDM symbol and the last DFT-s-OFDM symbolor CP-OFDM symbol.

Pre-DFT PTRS insertion may be performed for multi-user transmission. Abase PTRS pattern with cyclic shift values may be used, wherein a basePTRS pattern may be determined based on Ns, Nc, or locations of Ncchunks and its cyclic shifted version may have the same Ns and Nc whilethe location of Nc chunks may have an offset (e.g., time offset) fromthe base PTRS pattern. FIG. 8 shows an example of a base PTRS pattern(e.g., CS=0) and its cyclic shifted version of the base PTRS pattern.

A base PTRS pattern and its cyclic shifted versions of the base PTRSpattern may be used. A base PTRS pattern may be used, configured, ordetermined based on one or more scheduling parameters including at leastone of scheduled bandwidth, a number of PRBs, TTI length, DM-RSconfiguration, MCS level, and transport block size. The cyclic shiftvalue may be determined based on a WTRU-specific parameter or anindicator in the associated DCI.

The set of cyclic shift values may be configured via a higher layersignaling. Additionally or alternatively, the set of cyclic shift valuesmay be determined based on one or more of a base PTRS pattern, ascheduled bandwidth, and/or frequency location of the scheduledbandwidth.

The WTRU-specific parameter may include at least one of a WTRUcapability, a WTRU category, a WTRU-ID (e.g., C-RNTI, IMSI modulo X).WTRU-ID modulo Ncs may be used to determine the cyclic shift value. Ncsmay be a maximum number of cyclic shift values or a total number ofcyclic shift values. The DM-RS configuration may include at least one ofthe number of symbols used for DM-RS transmission, time/frequencylocations of DM-RS symbols, and/or DM-RS antenna ports number(s)indicated for a PUSCH transmission.

A zero-power PTRS may be used. For example, a WTRU may be indicated totransmit one or more zero-power PTRS when the WTRU is scheduled for aPUSCH transmission. Zero-power PTRS pattern may be determined based on abase PTRS pattern and its cyclic shifted versions. The WTRU may avoidsending a signal on the REs for zero-power PTRS.

FIG. 9 illustrates example WTRU-specific zero-power and non-zero-powerPTRS patterns with different CS values. The PUSCH REs for zero-powerPTRS may be punctured or rate-matched around. Reference signal sequencefor zero-power PTRS may be all zero values. The base PTRS pattern forzero-power PTRS pattern may be the same as non-zero power PTRS pattern,and cyclic shift values may be different between zero-power PTRS patternand non-zero-power PTRS pattern. The cyclic shift values for zero-powerPTRS pattern may be indicated as a part of scheduling parameters. Thecyclic shift values for zero-power PTRS patterns may be determined basedon the cyclic shift value(s) of non-zero-power PTRS patterns. The cyclicshift values for zero-power PTRS patterns may be determined based onDM-RS port number allocated for a PUSCH transmission. The base PTRSpattern and its cyclic shifted versions for zero-power PTRS may beseparately configured, e.g., via a higher layer signaling.

FIG. 10 illustrates example WTRU-specific OCC for PTRS tones within aPTRS chunk. An orthogonal cover code (OCC) may be used for the PTRS. Forexample, an OCC may be used for the PTRS tones within a chunk. The OCCmay be interchangeably used with orthogonal sequence, random sequence,PN sequence, Zadoff-Chu sequence, scrambling sequence, and/or golaysequence. The OCC may be determined based on chunk size and one or moreWTRU-specific parameter. For example, a first OCC (e.g., [1 1]) may beused for the PTRS tones in each chunk if WTRU-ID modulo 2 is ‘0’ and asecond OCC (e.g., [1 −1]) may be used for the PTRS tones in each chunkif WTRU-ID modulo 2 is ‘1’. The OCC parameter may be indicated in theassociated DCI. The OCC parameter may be determined based on one or morescheduling parameter. For example, OCC parameter for PTRS may bedetermined based on DM-RS configuration (e.g., DM-RS port). If a WTRU isconfigured with DM-RS port-0, the WTRU may use a first OCC (e.g., [1 1])and if a WTRU is configured with DM-RS port-1, the WTRU may use a secondOCC (e.g., [1 −1]). If OCC is based on a scrambling sequence, thescrambling sequence initialization may be based on WTRU-ID.

Post-DFT PTRS may be provided. The phase noise reference signals may beinserted into the IDFT block in a system transmitting using theDFT-s-OFDM waveform. One or more of the following may apply (e.g.,features relating to those illustrated in FIG. 11 and FIG. 12 ).

In examples puncturing may be provided. FIG. 11 illustrates an exampleof Post-DFT PNRS insertion via puncturing. Several outputs of the DFTblock are punctured and replaced with reference symbols.

In examples multiplexing may be provided. FIG. 12 illustrates an exampleof post-DFT PNRS insertion via multiplexing. The outputs of the DFTblock and reference symbols may be multiplexed and mapped to thecorresponding subcarriers.

The locations of the phase noise reference symbols illustrated in thefigures are exemplary locations and they may be mapped to differentinputs than shown. For example, PNRS may be mapped to the IDFT as shownin FIG. 13 , which illustrates an example of Post-DFT PNRS insertion viamultiplexing. The subcarriers used for the transmission of PNRS by aWTRU may be used by other WTRU(s) to transmit PNRS as well. In such acase, the PNRS from different WTRUs may need to be orthogonalized byusing spreading and/or orthogonal cover codes in time domain (e.g., overconsecutive OFDM symbols).

In examples, one or more PNRS types may be used for DFT-s-OFDM. Forexample, a first PNRS type may be used when a single-user MIMOtransmission is used and a second PNRS type may be used when amulti-user MIMO transmission is used, wherein the first PNRS type may bepost-DFT PNRS and the second PNRS type may be a pre-DFT PNRS.

The PNRS type (e.g., pre-DFT PNRS or post-DFT PNRS) or PNRS scheme(e.g., multiplexing or puncturing) for a DFT-s-OFDM transmission may bedetermined based on at one or more of following: the uplink M IMOtransmission mode or scheme used, the modulation order used, the channelcoding scheme used, the transport block size scheduled, the number ofresource block(s) scheduled, or the number of DFT-s-OFDM symbols used ina slot or a mini-slot.

An uplink MIMO transmission mode or scheme may be used. For example, aclosed-loop transmission scheme may use a first PNRS type/scheme and anopen-loop transmission scheme may use a second PNRS type/scheme.

A modulation order may be used. For example, a lower modulation order(e.g., QPSK and 16QAM) may use a first PNRS type/scheme and a highermodulation order (e.g., 64QAM) may use a second PNRS type/scheme.

A channel coding scheme may be used. For example, a first channel codingscheme (e.g., LDPC) may use a first PNRS type/scheme and a secondchannel coding scheme (e.g., polar) may use a second PNRS type/scheme.

A transport block size may be scheduled. For example, if a transportblock size is greater than a predefined threshold, a first PNRStype/scheme may be used; otherwise, a second PNRS type/scheme may beused.

PNRS with OFDM may be provided. The transmission of PNRS may be turnedon and off on a user basis. The number of PNRS may adaptively changedepending on the modulation order and/or other parameters. The number ofsubcarriers allocated to PNRS may change, which may result in a need toadaptively change the transport block size. In examples, the transportblock size may be kept constant, e.g., even when PNRS is turned on orthe number of PNRS is changed. Puncturing may be introduced to map thedata symbols to the available data subcarriers. An example is shown inFIG. 14 , which illustrates an example puncturing in OFDM for PNRSinsertion. The data symbols planned to be transmitted on thePNRS-carrying subcarriers may be punctured and replaced with PNRS, e.g.,when PNRS has to be transmitted.

Configuration of the puncturing and/or multiplexing patterns may beprovided. The PNRS multiplexing and/or puncturing patterns (e.g., thenumber of PNRS symbols in an OFDM symbol; which inputs of the DFT and orthe IDFT are used to feed in the PNRS, which OFDM symbols have PNRS) maybe configured by a central controller. The number of PNRS symbols in anOFDM symbol may be referred to as a frequency density of PNRS (or afrequency pattern of PNRS) and which OFDM symbols have PNRS may bereferred to as a time density of PNRS (or a time pattern of PNRS). Oneor more of the following may apply, e.g., for configuration of thepuncturing and/or multiplexing patterns.

The PNRS pattern or pattern subset may be determined based on one ormore of the following: Operating frequency band, MCS level (e.g.,modulation order and/or coding rate), numerology (e.g., subcarrierspacing and/or system bandwidth), higher layer signalling, scheduledbandwidth (or the number of PRBs scheduled), the number of layers forSU-MIMO transmission (e.g., transmission rank), MIMO mode of operation(e.g., SU-MIMO or MU-MIMO), waveform used (e.g., CP-OFDM or DFT-s-OFDM),and/or DM-RS density (e.g., front-loaded DM-RS only or front-loadedDM-RS with an additional DM-RS; number of OFDM or DFT-s-OFDM symbolsused for DM-RS).

All or a subset of PRBs may be used for PNRS transmission. When a subsetof PRBs carries PNRS, the subset of PRBs that carry PNRS may bedetermined based on one or more of following: DM-RS port or a set ofDM-RS ports allocated or indicated in an associated DCI or WTRU specificparameters. For example a DM-RS port or a set of DM-RS ports may beallocated or indicated in an associated DCI for MU-MIMO operation andthe set of PRBs which may carry PNRS may be determined based on theDM-RS port or the set of DM-RS ports allocated. Every 2nd PRB with a PRBoffset=0 may contain PNRS if a first DM-RS port (or a first set of DM-RSports) is indicated; every 2nd PRB with a PRB offset=1 may contain PNRSif a second DM-RS port (or second set of DM-RS ports) is indicated. AWTRU-specific parameter (e.g., WTRU-ID, C-RNTI, scrambling identity,scrambling identity of PNRS, etc.) may be provided. For example, a firstWTRU may transmit (or receive) every 2nd PRB of the scheduled PRBs witha PRB offset=0 while a second WTRU may transmit (or receive) every 2ndPRB of the scheduled PRBs with a PRB offset=1, where the PRB offset maybe determined based on WTRU-specific parameter.

For scheduled UL transmissions, the eNB may signal to the WTRU whichPNRS pattern to use. The eNB may signal this information to the WTRU forexample with the UL grant. One or more of the following of the followingmay apply: all the RBs allocated for UL transmissions (e.g., all the RBsallocated for UL transmissions) may be configured to carry at least onePNRS (e.g., when PNRS are fed into the IDFT); the possible patterns maybe pre-defined, e.g., the eNB may signal to the WTRU the index of thedesired pattern; the PNRS pattern to use may be determined (e.g.,implicitly) based on the number of allocated PRBs; and/or the PNRSpattern to use may be determined (e.g., implicitly) based on the MCSlevel indicated in the UL grant.

For scheduled DL transmissions, the eNB may signal to the WTRU whichPNRS pattern is used in the transmission. The eNB may signal thisinformation to the WTRU for example with the DL grant. One or more ofthe following may apply: the RBs allocated for DL transmissions (e.g.,all the RBs allocated for DL transmissions) may be configured to carryat least one PNRS (e.g., when PNRS are fed into the IDFT); the possiblepatterns may be pre-defined, e.g., the eNB may signal to the WTRU theindex of the desired pattern; the PNRS pattern to use may be determined(e.g., implicitly) based on the number of allocated PRBs; and/or thePNRS pattern to use may be determined (e.g., implicitly) based on theMCS level indicated in the UL grant.

For an UL transmission with DFT-s-OFDM and when the PNRS are fed intothe DFT block one or more of the following may apply. A continuous setof inputs of the DFT, e.g., starting with the lowest index, may be usedto transmit the PNRS. A continuous set of inputs of the DFT startingwith the highest index may be used to transmit the PNRS. A certain setof inputs of the DFT may be used to transmit the PNRS, e.g., wherein theset of inputs may be determined based on one or more of: predeterminedlocation; WTRU parameters (e.g., WTRU-ID), service type (e.g., URLLC,eMBB, and mMTC), etc.; or system parameter(s) (e.g., subframe number,radio frame number, cell-ID).

For an UL transmission with OFDM and when the PNRS are fed into the IDFTblock by puncturing or multiplexing one or more of the following mayapply. A first PRB of scheduled PRBs for an uplink transmission may beused to transmit a UL PNRS, e.g., wherein the first PRB may be the PRBwith a lowest index within the PRBs scheduled for a WTRU. In examples,the first PRB may be the PRB with a highest index within the PRBsscheduled for a WTRU. A certain PRB of scheduled PRBs for an uplinktransmission may be used to transmit a UL PNRS, e.g., wherein thecertain PRB may be determined based on one or more of: a predeterminedlocation (e.g., first or last PRBs in a schedule PRBs); WTRU-specificparameter(s) (e.g., WTRU-ID, service type (e.g., URLLC, eMBB, and mMTC);or system parameter(s) (e.g., subframe number, radio frame number,cell-ID). The first N subcarriers of the first PRB in the scheduled PRBsmay be used to transmit UL PNRS. The first N subcarriers of the last PRBin the scheduled PRBs may be used to transmit UL PNRS.

The multiplexing and/or puncturing pattern for the PNRS may beimplicitly determined, e.g., from the resource allocation. For example,the number of subcarriers allocated, the modulation order, and/or thetransport block size may be determined based on how many inputs of theDFT and/or the IDFT do not need to be used for data transmission. Theseinputs may (e.g., then) be used for PNRS transmission. The location ofthe PNRS (e.g., which inputs of the DFT and/or the IDFT to feed in thePNRS) may not be known implicitly, it may be pre-configured. Forexample, the first/last N inputs may be used to transmit PNRS. The PNRSmay be distributed over the allocated resources with a pre-determinedrule (for example uniformly, starting from index=0 of the resources).

The transport block size (e.g., of the data block to be transmitted) maydiffer based on the number of resources allocated for PNRS, for exampleif multiplexing of data and PNRS is used. The WTRU may determine theactual transport block size used for transmission from a nominaltransport block size signaled by the eNB and/or the PNRS configuration.As an example, assume the eNB signals to the WTRU to transmit a blocksize of N information bits using 16 QAM modulation and 1/2 coding rate,resulting in {(N×2)/log 2(16)}=N/2 subcarriers being used fortransmission (e.g., N/2 DFT size if DFT-s-OFDM is used). If K resources(e.g., subcarriers) over the duration of the subframe are reserved forPNRS, then the actual transport block size may be N−2K information bits.The same may apply to the determination of the transport block size inDL transmission.

PNRS may be used with multiple TRPs. One or more types of PNRS may beused. For example, a first type of PNRS may be common for (e.g., all)WTRUs (or shared by (e.g., all) WTRUs) in a cell while a second type ofPNRS may be a WTRU specific or a WTRU group specific. A first type ofPNRS may be transmitted in a predefined or a predetermined locationwhile a second type of PNRS may be transmitted via scheduledresource(s). The first type of PNRS may be used as a default PNRS. Thesecond type of PNRS may be used as a supplemental PNRS. The second typeof PNRS may be transmitted or presented based on one or more conditions.For example, the second type of PNRS may be present (or be transmitted)in a scheduled resource, e.g., based on one or more schedulingparameters. One or more of following may apply: if modulation order ishigher than a predefined threshold, the second type of PNRS may bepresent, for example, if a modulation order is higher than QPSK (e.g.,16QAM or 64QAM), the second type of PNRS may be present; or iftransmission rank is higher than a predefined threshold, the second typeof PNRS may be present.

One or more PNRS configurations may be transmitted or used. Theassociated PNRS for a demodulation may be determined based on downlinkchannel types. For example, two PNRS configurations may be used and afirst PNRS configuration may be associated with a downlink controlchannel and a second PNRS configuration may be associated with adownlink data channel. A PNRS configuration may include one or more oftime/frequency locations, associated transmission/reception point (TRP),reference signal power, scrambling code, scrambling ID, or periodicity.A first PNRS configuration may be associated with a downlink controlchannel (e.g., PDCCH) and a second PNRS configuration may be associatedwith a downlink data channel (e.g., PDSCH). The association between PNRSconfiguration and a downlink channel may be predetermined, configuredvia higher layer, or dynamically indicated. A first PNRS configurationmay be associated with a downlink control channel and one or more PNRSconfigurations may be associated with a downlink data channel.

Downlink control channel, PDCCH, and enhanced PDCCH (EPDCCH) may beinterchangeably used.

One or more PNRS configurations may be transmitted or used for adownlink signal transmission, wherein the one or more PNRS may be usedto demodulate the downlink signal. An associated PNRS may be indicatedto a WTRU for a downlink signal demodulation. For example, multiple PNRSconfigurations may be transmitted or used and one of the PNRSconfigurations may be associated for a physical downlink shared datachannel (PDSCH) which may be scheduled for a WTRU. For the PDSCHdemodulation, a WTRU may be indicated which PNRS configuration withinthe multiple PNRS configurations to use. One or more of the followingmay apply: the associated PNRS configuration for a downlink data channelmay be indicated; or the associated PNRS configuration for a controlchannel may be determined.

The associated PNRS configuration for a downlink data channel may beindicated one or more of following; an associated DCI that may be usedto schedule the PDSCH; a location of PDSCH scheduled, for example, thetime and/or frequency location of the scheduled PDSCH may determine theassociated PNRS configuration; a location of DL control channel searchspace wherein the associated DCI is received (for example, a DL controlchannel search space (SS) may be partitioned, each partitioned DLcontrol channel search space may be associated with a PNRSconfiguration, and/or, if a WTRU received a DCI in a certain partitionedDL control channel search space, the WTRU may know which PNRSconfiguration to use; or an RNTI used for the associated DCI maydetermine the associated PNRS configuration, for example, one or moreRNTI may be used for a DCI and each RNTI may be associated with aspecific PNRS configuration.

The associated PNRS configuration for a control channel may bedetermined based on one or more of following. A DL control search space(SS) may be partitioned and each partition of the DL control SS may beassociated with a specific PNRS configuration. A WTRU may use theassociated PNRS configuration for a partitioned DL control SS, e.g.,when the WTRU monitors the partitioned DL control SS. The associatedPNRS for each partition of DL control SS may be predetermined,configured, or signalled. One or more DL control decoding candidates maybe monitored in a DL control SS and (e.g., each) DL control decodingcandidate(s) may be associated with a specific PNRS configuration. Theassociated PNRS for (e.g., each) DL control decoding candidate(s) may bepredetermined, configured, or signalled. Time and/or frequency resourcesused for the DL control channel. For example, a first time/frequencyresource for a DL control channel may be associated with a first PNRSconfiguration and a second time/frequency resource for a DL controlchannel may be associated with a second PNRS configuration. Atime/frequency resource for a DL control channel may be referred to asan (E)PDCCH resource set. A (e.g., each) (E)PDCCH resource set may beassociated with a specific PNRS configuration. The association between(E)PDCCH resource set and PNRS configuration may be signaled,configured, or indicated in the configuration of (E)PDCCH resource. ThePNRS configuration may be preconfigured via higher layer signalling. A(e.g., each) PNRS configuration may be associated with an index.

FIG. 15 illustrates an example of PNRS and EPDCCH resource setassociation.

One or more operation modes may be used for a demodulation of downlinksignal with PNRS. For example, a WTRU may demodulate a downlink signalwith phase noise compensation based on a cell-specific PNRS in a firstoperation mode and the WTRU may demodulate a downlink with phase noisecompensation based on a WTRU-specific PNRS. If a WTRU is configured witha first operation mode, the WTRU may use a cell-specific PNRS fordownlink signal demodulation, wherein the cell-specific PNRS may belocated in a predetermined location. If a WTRU is configured with asecond operation mode, the WTRU may use a WTRU-specific PNRS fordownlink signal demodulation, wherein the WTRU-specific PNRS may belocated in a scheduled downlink resource.

One or more PRBs may be used to schedule a PDSCH and the one or morePRBs may be associated with one or more PNRS configurations. In anexample, each PRB may contain its associated PNRS, and a WTRU may usethe PNRS. The PNRS may be used for phase noise compensation. A separatereference signal for demodulation may be transmitted. For example, afirst reference signal (e.g., PNRS) may be used to estimate phase noiseand a second reference signal (e.g., DM-RS) may be used to estimatechannel; the estimated phase noise and/or estimated channel may be usedto demodulate downlink signal. The number of antenna ports for PNRS andthe number of antenna ports for DM-RS may be different. For example, asingle antenna port may be used for PNRS irrespective of thetransmission rank (e.g., number of layers for a downlink signaltransmission), and, the number of antenna ports for DM-RS may bedetermined based on the transmission rank (e.g., number of layers forthe associated downlink transmission). The number of PRBs associatedwith a PNRS configuration may be indicated, determined, or configured,e.g., via higher layer signaling. For example, a WTRU may be configuredthat 3 PRBs may be associated with a PNRS; the WTRU may assume that aPNRS may be transmitted in at least one of 3 PRBs associated with thesame PNRS; the WTRU may assume that a PNRS may be transmitted in asubset of PRBs associated with the same PNRS.

FIG. 16 illustrates an example of PNRS and PRB set association.

One or more PRB groups (PRG) may be used to determine the associationbetween PRB and PNRS. A PRG may be defined as a set of consecutive PRBsin a subframe and the number PRGs in a subframe may be determined basedon the total number of PRBs in a system bandwidth and the number ofconsecutive PRBs in a PRG. For example, if the total number of PRBs in asystem bandwidth is 50 and the number of PRBs in a PRG is 5, then 10PRGs may be used in a subframe. Each PRG may contain a PNRS. Forexample, a first PRB in a PRG may contain the PNRS. A WTRU may bescheduled with one or more PRBs in a subframe. The WTRU may use the PNRSlocated in the first PRB of the PRG for demodulation of a PRB located inthe PRG. A PRG may be associated with a TRP (or cell) and (e.g., each)PRG may be associated with a specific TRP (or cell). The number of PRBsfor a PRG may be configurable. The PRG size may be the same as the totalnumber of PRBs (e.g., a single TRP is used).

The PNRS transmissions may be turned on and off dynamically by the eNB.A WTRU may request the transmission of PNRS. The PNRS transmissions maybe WTRU-specific or common. When it is common, the time/frequencyresources reserved for its transmissions may be configured by the eNB.When it is WTRU-specific, the eNB may signal the WTRU of the PNRStransmission.

PNRS for UL transmission may be disclosed. A WTRU may be configured forPNRS transmissions in UL, for example to allow the eNB to perform phasetracking to correct for the WTRU transmitter phase noise.

For the PNRS configuration of the UL transmissions, one or more of thefollowing may apply: the presence or use of a PNRS may be determined;the density of a PNRS (e.g., one subcarrier, two subcarrier, etc.) maybe determined; the UL PNRS may be transmitted in one or more subcarrierswithin a scheduled uplink resources (e.g., PRBs); the UL PNRS may betransmitted in one or more sub-carriers of an OFDM symbol (and inconsecutive OFDM symbols of the RB); the index of the sub-carrierswithin an RB, used for UL PNRS transmissions, may be predefined; or forscheduled UL transmissions using multiple RBs, the eNB may signal to theWTRU which RB may carry the PNRS.

The presence or use of a PNRS may be determined based on an operatingfrequency band. For example, a UL PNRS may not be used in a loweroperating frequency band (e.g., lower than 6 GHz) and a UL PNRS may beused in a higher operating frequency band (e.g., higher than 6 GHz). AWTRU may determine the use or transmission of a PNRS based on theoperating frequency band. The use or transmission of a PNRS may beindicated from an eNB.

The density of a PNRS (e.g., one subcarrier, two subcarrier, etc.) maybe determined based on one or more of following: operating frequencyband; MCS level (e.g., modulation order and/or coding rate); Numerology(e.g., subcarrier spacing and/or system bandwidth); higher layersignaling, for example, the association between the PNRS density and MCSlevel may be determined based on a higher layer signaling, and the PNRSdensity for a PDSCH or PUSCH transmission may be determined based on MCSlevel indicated in an associated DCI; scheduled bandwidth (e.g., numberof PRBs scheduled); MIMO mode of operation (e.g., SU-MIMO or MU-MIMO);and/or number of layers (e.g., transmission rank).

The UL PNRS may be transmitted in one or more subcarriers within ascheduled uplink resources (e.g., PRBs). A first PRB of a scheduled PRBsfor an uplink transmission may be used to transmit a UL PNRS, whereinthe first PRB may be the PRB with a lowest index within the PRBsscheduled for a WTRU. The first PRB may be the PRB with a highest indexwithin the PRBs scheduled for a WTRU. A certain PRB of scheduled PRBsfor an uplink transmission may be used to transmit an UL PNRS, whereinthe certain PRB may be determined based on one or more of: predeterminedlocation (e.g., first or last PRBs in a schedule PRBs); WTRU parameters(e.g., WTRU-ID, scrambling-ID, virtual ID), service type (e.g., URLLC,eMBB, and mMTC); or system parameters (e.g., subframe number, radioframe number, cell-ID). A first subcarrier of the first PRB in thescheduled PRBs may be used to transmit a UL PNRS. A first N subcarriersof the first PRB in the scheduled PRBs may be used to transmit an ULPNRS.

The UL PNRS may be transmitted in one or more sub-carriers of an OFDMsymbol, and, in consecutive OFDM symbols of the RB. An OFDM symbol maybe interchangeably used with SC-FDMA symbol, DFT-s-OFDM symbol, UWDFT-s-OFDM symbol, and ZT DFT-s-OFDM symbol.

The index of the sub-carriers within an RB, used for UL PNRStransmissions, may be predefined, e.g., it may be the center sub-carrierof the RB. One or more of following may apply for the UL PNRS subcarrierlocation (and/or PRB location).

For scheduled UL transmissions using multiple RBs, the eNB may signal tothe WTRU which RB may carry the PNRS. Some RBs may not carry the PNRS,for example to reduce the RS overhead. The eNB may signal thisinformation to the WTRU for example with the UL grant. One of thefollowing may apply: RBs (e.g., all the RBs) allocated for ULtransmissions are configured for PNRS; or a pattern of RBs that may beconfigured with PNRS may be pre-defined, e.g., the eNB may (e.g., only)need to signal to the WTRU the index of the desired pattern.

A PNRS may be used to demodulate an associated data. For example, a PNRStransmitted in a certain PRB may be used to demodulate the data in thesame PRB. One or more of following may apply. A PNRS may be transmittedin one or more of PRBs scheduled for a WTRU and a WTRU (or eNB) maytransmit DM-RS in (e.g., each) PRBs, which may be except for the one ormore PRB containing a PNRS. The DM-RS may be signaled based on a firstreference signal pattern (e.g., distributed within a PRB). The PNRS maybe signaled based on a second reference signal pattern (e.g., localizedwithin a PRB). The DM-RS locations in the one or more PRBs containing aPNRS may be used for data transmission. The DM-RS may be transmitted inthe one or more PRBs containing a PNRS, e.g., if the transmission rank(e.g., number layers) for data is higher than 1. A PNRS may betransmitted in one or more of PRBs scheduled for a WTRU, and, a WTRU (oreNB) may transmit different types of DM-RS based on the presence of aPNRS in a PRB. For example, if a scheduled PRB contains a PNRS a firsttype of DM-RS may be used, otherwise a second type of DM-RS may be used.The reference signal pattern of first type of DM-RS may be differentform that of the second type of DM-RS. The first type of DM-RS may havea lower density (e.g., smaller number of REs) than the second type ofDM-RS.

The eNB may estimate the rate of change of the transmitter phase noise(for example based on eNB phase offset measurements using the defaultPNRS setting), and may configure the WTRU for an alternate PNRS pattern,for example a lower density pattern (e.g., as illustrated in FIG. 4 ).

Data demodulation reference signal (DM-RS) transmission is disclosed. Insome frame structures, the DM-RS may be transmitted at the beginning ofthe frame/sub-frame/packet, e.g., before the data transmissions starts.If no DM-RS is transmitted in the OFDM symbols carrying data, channelestimation accuracy may suffer, e.g., especially in high mobilityscenarios.

Distributed DM-RS symbols may be mapped to the data part of theframe/sub-frame/packet, e.g., in addition to the DM-RS symbols at thebeginning of the sub-frame, which may be for both DL and ULtransmissions, e.g., to mitigate the degradation of the channelestimates due to high mobility. FIG. 17 illustrates an example ofdistributed DM-RS mapped to the control/data part of the sub-frame. Thedistributed DM-RS may be dynamically signaled or semi-staticallyconfigured by the eNB.

The distributed DM-RS may be mapped to the data part of the sub-framewith a higher or lower density of reference signals, for example as afunction of mobility: for higher mobility scenarios, a higher densitypattern may be used (for example as shown in FIG. 17 ), while for low tomedium mobility, a lower density pattern may be used.

The type of distributed DM-RS pattern may be dynamically configured bythe eNB. For example, several distributed DM-RS patterns may be defined,for example: “None,” “Low Density,” and/or “High Density.” For DLtransmissions, the pattern type may be signaled by the eNB to the WTRUwithin the control channel, e.g., in the DCI, and the pattern may beapplied for the DL assignment associated to that DCI. For ULtransmissions, the pattern type may be dynamically configured by the eNBvia the DL control channel. In this case, the WTRU may apply the patternto the transmission (e.g., sub-frame/TTI) indicated by the UL grant.

For the DL and the UL transmissions, the configured DM-RS pattern may becell-specific, or WTRU specific.

When distributed DM-RS is enabled, some of the time/frequency resourcesmay need to be taken from the data transmissions and allocated to DM-RStransmission. The transport block size may be kept constant, e.g.,regardless of the type of distributed DM-RS pattern configured: toaccount for the different number of available resource elements (REs),and/or rate matching patterns may be defined to be associated to eachdistributed DM-RS pattern type. For example, when configured for a highdensity distributed DM-RS pattern type, the WTRU may select thecorresponding rate matching pattern to apply (e.g., for the signaledTBS). The rate matching pattern may be kept the same, e.g., regardlessof the DM-RS pattern type, and different sets of transport block sizesmay be defined, associated to each distributed DM-RS pattern type. Basedon the selected DM-RS pattern type, the corresponding TBS table may beused.

For systems using Non-Orthogonal Multiple Access (NOMA), whereby anumber of WTRUs may be assigned for transmission in the sametime/frequency resources, the same distributed DM-RS pattern type may beconfigured for WTRUs (e.g., all WTRUs) in the same NOMA group, forexample to prevent data—RS collisions. The WTRUs in that NOMA group maybe configured with the same distributed DM-RS pattern type viaindividual signaling of WTRU specific DM-RS pattern, or using a group ID(such as a group RNTI) to simultaneously configure WTRUs (e.g., allWTRUs) in the group.

PNRS and DM-RS may be associated. One or more DM-RS ports may be usedfor a PDSCH or a PUSCH transmission. The number of DM-RS ports used fora PDSCH or a PUSCH transmission may be determined based on the number oflayers used, allocated, or determined for a PDSCH or a PUSCHtransmission, wherein the number of layers may be referred to as atransmission rank. One or more of following may apply: the number oflayers for a PDSCH or a PUSCH transmission may be indicated in anassociated DCI; the presence and/or PNRS density may be determined basedon the number of layers indicated for a PDSCH or a PUSCH transmission;the presence and/or PNRS density may be determined based on one or morescheduling parameters not including the number of layers; and/or thenumber of PNRS ports (or PNRS density) may be determined based on thenumber of codewords used, scheduled, or determined for a WTRU.

The number of layers for a PDSCH or a PUSCH transmission may beindicated in an associated DCI. The set of DM-RS ports may be determinedbased on one or more of the number of layers, an indication of MU-MIMOoperation, an indication of a set of DM-RS ports associated with thenumber of layers, or an indication a set of DM-RS ports. The number ofOFDM symbols used for DM-RS may be determined based on the number oflayers indicated.

The presence and/or PNRS density may be determined based on the numberof layers indicated for a PDSCH or a PUSCH transmission. For example,one or more of following may apply. A single PNRS port may betransmitted or used if the number of layers is lower than a predefinedthreshold; more than one PNRS port may be transmitted or used if thenumber of layer is higher than the predefined threshold. The number ofPNRS ports may be transmitted or used as the number of DM-RS ports;one-to-one mapping between PNRS ports and DM-RS ports, wherein the DM-RSport and the PNRS port mapped may be considered as quasi-collocated(QCL-ed) in terms of at least one of QCL parameters (e.g., delay spread,Doppler spread, frequency shift, average receive power, spatial Rxparameters, etc.).

The presence and/or PNRS density may be determined based on one or morescheduling parameters not including the number of layers. A single PNRSport may be transmitted or used. The PNRS port may be associated (orQCL-ed) with a certain DM-RS port. The DM-RS port associated with thePNRS may be predefined, predetermined, or indicated in the associatedDCI. For example, the first DM-RS port within the set of DM-RS portsused for a WTRU may be associated with the PNRS.

The number of PNRS ports (or PNRS density) may be determined based onthe number of codewords used, scheduled, or determined for a WTRU. Forexample, a single PNRS port may be used if a WTRU is scheduled with asingle codeword while two PNRS ports may be used if a WTRU is scheduledwith two codewords. The number of codewords may be determined based onthe number of layers indicated in the DCI. The number of codewords maybe determined based on the number of DCIs a WTRU may receive. Forexample, a WTRU may receive one or more DCIs and each DCI may beassociated with a codeword. The presence and/or density of PNRS of eachcodeword may be determined based on one or more of the schedulingparameters of each codeword. A WTRU may receive two DCIs for PDSCHtransmission, and a DCI may be associated with a codeword and includesscheduling parameters of each codeword. The presence and/or density ofthe PNRS for each codeword may be determined based on one or more of MCSlevel selected, the number of PRBs scheduled, number of layers, andDM-RS density of each codeword. PNRS presence and/or density (includingzero density) for a codeword may be determined based on the QCL statusbetween DM-RSs of one or more codewords. For example, DM-RSs of thecodewords scheduled are QCL-ed, PNRS may be transmitted in a subset ofcodewords (e.g., a single codeword only includes PNRS); while if DM-RSsof scheduled codewords are non-QCL-ed, the PNRS presence and/or densitymay be determined based on the associated DCI or scheduling parameter ofcodeword.

In examples, one or more PNRS may be transmitted or received and a(e.g., each) PNRS may be associated with a DM-RS port. A PNRS patternmay be used in an PRB (or PRB-pair) and all or subset of scheduled PRBsmay include the PNRS pattern. A PNRS (or a PNRS pattern, a PNRS port) inan PRB may be associated (or QCL-ed) with a DM-RS port or a set of DM-RSports, which DM-RS port or a set of DM-RS ports associated with the PNRSin an PRB may be determined based on one or more of following: thenumber of layers (or the number of DM-RS ports); the number of PRBsscheduled (or a scheduled bandwidth); the number of PNRS ports (or thenumber of subcarriers used for PNRS within an PRB); and/or the PRB indexor PRB location (n-th PRB) within the scheduled PRB.

A UCI may be transmitted on PUSCH with or without data. The UCI mayinclude at least one of channel state information (e.g., CQI, PMI, RI,and CRI, etc.) and HARQ-ACK information (e.g., ACK or NACK). One or morechannel state information (CSI) types may be used. A CSI type may beassociated with a CSI parameter. A CSI parameter may include one or moreof, a CQI (channel quality indicator), a wideband CQI, a subband CQI, aCQI for a first codeword, and/or a CQI for a second codeword, a PMI(precoding matrix indicator), a wideband PMI, a subband PMI, a PMI for afirst component codebook (e.g., i1), a PMI for a second componentcodebook (e.g., i2); a multi-component codebook structure W1W2, (e.g.,W1 may be the first component codebook and W2 may be the secondcomponent codebook), a CRI (e.g., CSI-RS resource indicator), a RI (rankindicator) and/or a PTI (precoding type indicator).

One or more HARQ-ACK information types may be used. A HARQ-ACKinformation type may be associated with a number of HARQ-ACK bits and/orcodeblock groups (CBGs). For example, a HARQ-ACK information type may beassociated with a single bit HARQ-ACK. A HARQ-ACK information type maybe associated with a two bit HARQ-ACK. A HARQ-ACK information type maybe associated with codeblock groups (CBGs). A HARQ-ACK information typemay be associated with a transport block. A transport block may have oneor more CBGs.

One or more UCI parts may be used. A UCI part may include one or moreCSI types and/or HARQ-ACK information type. A UCI may be codedseparately and transmitted simultaneously. A first UCI part may includeone or more CSI types. The first UCI part may have a constant payloadsize irrespective of values that may be determined for the one or moreCSI types. For example, CRI, RI, PTI, and a CQI for a first codeword maybe a first UCI part. A second UCI part may include one or more CSItypes. The second UCI part may have a variable payload size that may bedependent on one or more CSI values in the first UCI part. For example,PMIs and CQIs of a second codeword may be a second UCI part and itspayload size may be determined based on RI value of the first UCI part.A third UCI part may include one or more HARQ-ACK information types.

One or more PTRS patterns and/or PTRS types may be used. A PTRS patternand/or PTRS type for a PUSCH transmission may be determined based on atleast one of a number of REs required for a UCI transmission or aspecific UCI part transmitted.

A PTRS pattern and/or PTRS type for a PUSCH transmission may bedetermined based on the number of REs required for a UCI transmission(Nre). For example, if Nre is smaller than a predefined threshold (a), afirst PTRS pattern may be used; otherwise, a second PTRS pattern may beused. More than one threshold may be used with multiple PTRS patterns.Nre may be associated with a specific UCI part. For example, the Nre maybe counted only for a subset of UCI parts (e.g., a first UCI part or athird UCI part). A PTRS pattern may be determined based on the ratiobetween available REs for a PUSCH transmission (e.g., Npusch) and Nre.For example, if the ratio of Nre/Npusch is less than a predefinedthreshold, a first PTRS pattern may be used; otherwise, a second PTRSpattern may be used. The ratio may be determined based on Nre/Npusch orNpusch/Nre. Npusch may be a number of available REs for PUSCHtransmission. The available REs may not include one or more of referencesignal (e.g., DM-RS and SRS), and UCI Res. Npusch may be a nominalnumber of REs. The nominal number of REs may be determined based on thescheduled bandwidth and/or TTI length (or slot length).

Table 1 shows an example of PTRS pattern determination based on at leastone of Nre or Nre/Npusch. PTRS pattern determination may be based on arequired number of REs for UCI (Nre) and/or ratio between Nre and thenumber of available REs for a PUSCH transmission.

TABLE 1 PTRS pattern Nre Nre/Npusch PTRS pattern-1 Nre ≤ α₁ Nre/Npusch ≤α₁ PTRS pattern-2 α₁ < Nre ≤ α₂ α₁ < Nre/Npusch ≤ α₂ . . . . . . . . .PTRS pattern-N α_(N-1) < Nre ≤ α_(N) α_(N-1) < Nre/Npusch ≤ α_(N)

A PTRS pattern and/or PTRS type for a PUSCH transmission may bedetermined based a specific UCI part transmitted. For example, a firstPTRS pattern may be used if a first UCI part and/or a second UCI partare transmitted on PUSCH; a second PTRS pattern may be used if a thirdUCI part is transmitted on PUSCH. A PTRS pattern may be different when aset of UCI parts transmitted on PUSCH. A PTRS pattern may be determinedbased on whether UCI includes HARQ-ACK information type or not. Forexample, a first PTRS pattern may be used if HARQ-ACK information typeis not included in the UCI, otherwise a second PTRS pattern may be usedfor a PUSCH transmission. A PTRS pattern and/or PTRS type for a PUSCHtransmission may be determined based on presence of UCI in the PUSCHtransmission. For example, a first PTRS pattern (e.g., a first PTRSdensity) may be used if a UCI is present on a PUSCH transmission and asecond PTRS pattern (e.g., a second PTRS density) may be used if no UCIis present on a PUSCH transmission.

Table 2 shows an example of PTRS pattern determination based on whichUCI part is transmitted on PUSCH. PTRS pattern determination may bebased on presence of one or more UCI parts in PUSCH.

TABLE 2 UCI part 1 UCI part 2 UCI part 3 PTRS pattern in PUSCH? inPUSCH? in PUSCH? PTRS pattern-1 No No No PTRS pattern-2 Yes Yes No . . .. . . . . . . . . PTRS pattern-N Yes Yes Yes

Sounding reference signal (SRS) transmission is disclosed. Soundingreference signal (SRS) transmission may include one or more of thefollowing: Sub-band SRS or SRS Transmission and RE Muting for SRS.

FIGS. 18&19 illustrate an example of Tx/Rx beam sweeping based on SRS.FIG. 20 illustrates an example of SRS transmission for beam measurement.FIG. 21 illustrates an example of SRS transmission with subband hopping.

Sub-band SRS is disclosed. Since the same waveform may be used for DLand UL (e.g., in NR), a common design for CSI-RS and SRS may bebeneficial. Sounding reference signals may be used for channel qualityestimation and/or beam measurement. Since the number of transmitter andreceiver beams to be measured may be multiple, a multi-shot SRStransmission may be used. Multi-shot may mean that SRSs (e.g., a set ofSRSs) are transmitted over a set of OFDM symbols that may be consecutiveOFDM symbols and/or that may follow a sequence or pattern in time(and/or frequency) that may be configured, determined and/or known. TheSRS transmitted in each of the OFDM symbols may be the same ordifferent. As an example, in FIG. 18 , the WTRU is transmitting the sameSRS while the eNB is sweeping its receive beam, and, FIG. 19 the WTRU issweeping its SRS, e.g., the WTRU is sweeping the beam it uses for thetransmission of SRS.

The sequence or pattern may be configured or determined in terms of atleast one of a symbol or symbols, a slot (e.g., a timeslot) or slotsand/or a mini-slot or mini-slots. The sequence or pattern may be afunction of a burst time, e.g., a beam or synchronization signal bursttime, a time window (e.g., a beam time window), or a time block (e.g.,beam time block). The burst time, time block, or time window may be anamount of time (e.g., continuous amount of time). The burst time, timeblock, or time window may be an amount of time (e.g., continuous amountof time) during which a beam direction may be used for transmission orreception. For example, a direction may not change during a burst time,time window, or time block, possibly excluding a transition time at thebeginning and/or end of the burst time, time window, or time block.

In an example, a WTRU may transmit a multi-shot SRS. A multi-shot SRSmay be a set of SRSs transmitted in one or more symbols in each of a setof burst times, time windows, or time blocks. The transmission may beaccording to configuration that may be provided by a eNB ((e.g., gNB)eNB and gNB may be used interchangeably) or other network entity.

A WTRU may not be able to transmit the SRS over the whole band, e.g.,due to the power limitation. It may be preferable for a WTRU to transmitSRS over a subband in a given time interval and time-multiplex thetransmission of SRS over different subbands. As an example, in FIG. 20 ,the SRS is transmitted on the same subband to enable beam measurementwhile in FIG. 21 the SRS is transmitted on different subbands to sound alarger bandwidth.

A beam measurement reference signal (BRS) may be configured to be aspecial case of CSI-RS for downlink and SRS for uplink. For example, theBRS may be configured to be a CSI-RS or SRS to be transmitted on aspecific antenna port. The resource allocation for the BRS (and/or SRS)may define a time and/or frequency resource allocation and may beconfigured by the eNB.

SRS transmission and RE muting for SRS is disclosed. A resource element(RE) may be or may correspond to a time and/or frequency resource or aset of time and/or frequency resources. For example, a RE may be or maycorrespond to a set of symbols (e.g., one or more symbols) and a set offrequencies or sub-carriers (e.g., N frequencies or subcarriers). Thefrequencies or subcarriers may be a subset of frequencies or subcarrierswithin a transmission band or bandwidth.

SRS may be transmitted, e.g., by a WTRU, in a set of REs that may bedistributed across a system bandwidth or across a sub-band of a systembandwidth. SRS may be transmitted in one or more symbols that may or maynot be adjacent in time. In an example, an RE may correspond to onesymbol and N subcarriers. An SRS may be transmitted in a set of REswhere the REs in which to transmit may be configured.

For example, a WTRU may receive a configuration of one or more, e.g., S,RE sets, in which SRS may be transmitted by the WTRU (e.g., first WTRU)and/or another WTRU (e.g., second WTRU). The configuration for a set ofREs may include identification of a set of REs in a band or sub-band.The configuration for a set of REs may include identification of a setof REs in a part of a band or sub-band that may be repeated in the bandor sub-band.

At least one of the following may be configured or indicated (e.g., aWTRU may receive a configuration or indication for at least one of thefollowing): a set of S REs sets; an RE set that may be used for SRStransmission, for example in a time period (e.g., subframe or TTI) suchas a current or upcoming time period; a number of symbols (e.g.,consecutive symbols) in which an SRS (e.g., multi-shot SRS) may betransmitted (e.g., the number of symbols may be configured for one ormore sets (e.g., for a set (e.g., individually for each set) or once forall sets or a subset of the sets)); a spacing (e.g., in time or symbols)between symbols for multi-shot transmission; a spacing in burst times,time blocks, or time windows between SRS transmissions or sets of SRStransmissions; a pattern of burst times, time blocks or time windows forSRS transmission, for example that may enable the WTRU to determine theburst times, time blocks, and/or time windows during which to transmitSRS (e.g., to transmit SRS in one or more symbols); or whether or not tochange (e.g., sweep) and/or how often to change its transmission beam ordirection during an SRS transmission (e.g., during a multi-shot SRStransmission).

Subframe may be used herein as an example of a time unit. Another unitmay be used and still be consistent with this disclosure. For example,in the examples described herein, slot (e.g., timeslot) or mini-slot maybe substituted for subframe and still be consistent with thisdisclosure.

An RE set may be configured with a periodicity.

A configuration or indication may be provided (e.g., by an eNB) and/orreceived (e.g., by a WTRU) semi-statically, (e.g., via higher layersignaling such as RRC signaling) or dynamically, for example by physicallayer signaling such as in DL control information (DCI) or with a grantsuch as an UL grant.

A WTRU may receive an indication (e.g., a trigger) to transmit SRS, forexample dynamically. The indication may be referred to herein as anSRS-trigger. The SRS-trigger may be provided (e.g., by an eNB) and/orreceived (e.g., by a WTRU) for example in or with an UL grant. TheSRS-trigger may be received in DL control information (DCI), for examplein a DCI format that may be or may include an UL grant. A WTRU maytransmit SRS based on the receipt of the SRS-trigger. The WTRU maytransmit SRS in the time period (e.g., subframe or TTI) in which theWTRU may transmit an UL channel (e.g., PUSCH) for which the grant wasreceived.

A WTRU may receive an indication of at least one set of REs on which totransmit SRS. The indication of a set may identify which set among Sconfigured sets to use. The WTRU may transmit SRS on an RE set, forexample based on receipt of an SRS-trigger and of an RE set on which totransmit SRS. The WTRU may transmit the SRS in the configured orindicated symbols.

In an example, a WTRU may receive a configuration of S RE sets. The WTRUmay receive an SRS-trigger, for example in or with an UL grant, and aconfiguration or indication to transmit SRS using one or more RE setsthat may be a subset of the S RE sets. The indication may identify theRE sets by index or other identifier with respect to the S RE sets. Theindication may identify the RE sets explicitly.

The WTRU may receive an UL grant and/or SRS-trigger in time period n.The WTRU may transmit a PUSCH and/or an SRS in time period n+k, forexample based on receipt of the UL grant and/or SRS-trigger in timeperiod n. The WTRU may transmit the SRS on the one or more RE sets, forexample when transmitting the SRS in time period n+k. The WTRU maytransmit the SRS on the one or more RE sets in multiple symbols (orother time periods), for example when multi-shot SRS is used. A hoppingpattern may be used such that a first set of RE sets may be used for SRStransmission in a first symbol or other time period and a second set ofREs may be used for SRS transmission in a second symbol or other timeperiod, for example when multi-shot SRS transmission is used. The delayfrom receiving an SRS-trigger to SRS transmission and the delay fromreceiving an UL grant to PUSCH transmission may be the same ordifferent.

When transmitting (e.g., a signal or channel) in a time period in whichan SRS is transmitted, a WTRU may mute its transmission in the REs thatmay be used for the SRS transmission. The WTRU may mute its transmissionby rate matching around the REs that are used for the SRS transmission.

A WTRU may rate match around REs that are used for SRS, for example in asymbol. For example, when a WTRU transmits (e.g., a channel or signal)in a symbol that is used for SRS by that WTRU or another WTRU, the WTRUmay rate match its transmission around the REs that are used for SRS.For example, a WTRU may rate match a data channel (e.g., PUSCH)transmission or a control channel (e.g., PUCCH) transmission around REsthat are used for SRS transmission. PUSCH and PUCCH may be used asexamples of channels that a WTRU may transmit. Another channel(s) may beused consistent with this disclosure.

A WTRU may rate match around the REs in an RE set that the WTRU may usefor SRS transmission. In an example, a WTRU may transmit a PUSCH and anSRS in a same time period, for example when a WTRU receives an UL grantand an SRS-trigger together. When transmitting the PUSCH, the WTRU mayrate match around the one or more sets of REs it uses for the SRStransmission.

To rate match (e.g., rate match a transmission) around a set of REs maymean to not map coded bits (e.g., of the transmission) to the set ofREs. For example, when mapping coded bits of a PUSCH to the REs in atime period, the WTRU may skip over the REs that are used for SRStransmission (e.g., that the WTRU or another WTRU may use for SRStransmission) in that time period. A time period may, for example, be asymbol or subframe.

A first WTRU may receive configuration of one or more RE sets that asecond WTRU may use for SRS transmission in a time period. Theconfiguration may be provided in or with an UL grant that is received bythe first WTRU. The configuration may be provided, for example, in DLcontrol information (DCI) or a DL control channel. The DCI or DL controlinformation may be separate from the DCI or DL control channel for thefirst WTRU's UL grant.

A first WTRU may rate match around the REs in an RE set that a secondWTRU may use for SRS transmission. A configuration or indication of theRE set that may be used for SRS transmission by the second WTRU may beprovided to and/or received by the first WTRU, for example in, with,and/or separately from an UL grant for the first WTRU.

In an example, a first WTRU may receive an UL grant to transmit a PUSCHin a time period. The WTRU may receive an indication that at least asecond WTRU may transmit SRS in the same time period. The WTRU mayreceive a configuration or indication of a set of REs on which at leasta second WTRU may transmit SRS. When transmitting the PUSCH, the WTRUmay rate match around the REs that may be used by at least the secondWTRU for SRS.

The number of bits that may be transmitted per RE may affect the power aWTRU may need or use to transmit a channel or signal such as PUSCH, forexample to achieve a certain or desired performance. The number of REsavailable for a transmission may affect the power the WTRU may need oruse.

A first WTRU may determine or adjust its transmit power for a channel orsignal (e.g., PUSCH, PUCCH, SRS, transmit power) or a set of channelsand/or signals based on the REs available for the transmission. A WTRUmay determine the number of available REs and set or adjust the powerbased on at least the number of available REs.

One or more of the following REs may be considered (e.g., by a firstWTRU) as unavailable REs (e.g., in a time period), for example whendetermining the available REs for a transmission (e.g., in a timeperiod) and/or when determining the power for the transmission (e.g., inthe time period): REs that may be used for SRS transmission; REs thatmay be used for DMRS, e.g., by the first WTRU; or REs that may be usedfor UL control information (UCI) transmission, for example when thetransmission of the UCI may be piggybacked on a PUSCH transmission.

A RE or set of REs that may be considered unavailable by a first WTRUmay be an RE or set of REs that may be used by the first WTRU or thesecond WTRU, e.g., for another channel or signal.

The WTRU may determine a power independent of available REs if thenumber of unavailable REs is below a threshold, e.g., that may beconfigured.

When determining SRS power, the determination may be based on at leastthe number of REs that may be used for the SRS transmission.

A WTRU may be configured with semi-persistent scheduling (SPS), forexample for an UL transmission. SPS may provide a WTRU with a grant orallocation for resources in the UL that it may use over multiple periodsof time (e.g., multiple slots or subframes), for example withoutreceiving an additional grant (e.g., for new data). In some of thosetime periods, at least some of the resources used or allocated for theSPS transmission may be used by a WTRU (e.g., another WTRU) for SRS.

An example of SRS transmission and RE muting is shown in FIG. 22 . Afirst WTRU may receive an SRS configuration that may be used for SRStransmission by the first WTRU or a second WTRU.

The first WTRU may receive an indication that indicates when another(e.g., a second) WTRU may transmit SRS, for example according to an SRSconfiguration such as an SRS configuration described herein. The SRSconfiguration may, for example, provide a set or sets of symbols and/orREs. The SRS configuration may, for example, provide a time and/orfrequency pattern.

The first WTRU may transmit in the UL (e.g., an UL data channel such asPUSCH). The first WTRU may mute (e.g., blank) and/or rate match aroundone or more REs and/or or symbols in which another WTRU may transmitSRS, for example according to a configuration, e.g., SRS configuration,the first WTRU may receive.

The first WTRU may receive an indication that may indicate when the SRSconfiguration, muting, and/or rate matching may be active and/or notactive. The first WTRU may receive an indication that may indicate whenit should perform the muting or rate matching and/or not perform themuting and/or rate matching. The indication may be received in at leastone of RRC signaling, MAC signaling, or physical layer signaling.

The SRS configuration, muting, and/or rate-matching may be activatedand/or deactivated, e.g., based on a received indication. The SRSconfiguration, muting, and/or rate matching may be for a specific ULtransmission (e.g., of an SPS configuration), a duration, a time window,and/or until deactivated. A specific UL transmission, duration, and/ortime window, may be relative to when the activation request is received,for example specific to time unit n+k for an activation request receivedin time unit n.

Activation/deactivation may be used to represent activation and/ordeactivation. Enabled and activated may be used interchangeably.Disabled and deactivated may be used interchangeably.

In examples, activation/deactivation of an SRS configuration, muting,and/or or rate matching may be provided in a MAC-CE. In examples,activation/deactivation of an SRS configuration, muting, and/or or ratematching may be provided in physical layer signaling such as in a DCIformat that may be scrambled (e.g., that may have its CRC scrambled)with a C-RNTI (e.g., SPS C-RNTI), e.g., that may be configured forand/or associated with the SPS configuration or transmission.

A WTRU may mute and/or rate match around one or more resources (e.g.,REs and/or symbols) based on or in response to receipt of an activationor indication for at least one of an SRS configuration, resource muting,and/or SRS rate matching around.

Semi-persistent SRS may be provided.

A WTRU may and/or may be configured to transmit SRS, e.g., multi-shotSRS. A WTRU may receive a configuration for SRS transmission. A WTRU mayreceive an activation and/or deactivation for SRS transmission.

A WTRU may transmit SRS, for example according to at least a receivedconfiguration. A WTRU may transmit, e.g., begin transmitting, SRS inresponse to receiving an SRS activation. A WTRU may not transmit, e.g.,may stop transmitting SRS, in response to receiving an SRS deactivation.

In an example an SRS activation and/or SRS deactivation may be providedand/or received in a MAC Control Element (e.g., MAC-CE).

A MAC-CE may be received in a PDSCH. A WTRU that mis-detects a MAC-CE todeactivate SRS transmission may continue transmitting SRS until the gNBrecognizes the mis-detection and sends another deactivation, e.g., thatmay be successfully received by the WTRU that deactivates SRStransmission.

A WTRU may be configured with a time window or other parameter that maylimit the number of SRS transmissions and/or the time during which theWTRU may transmit SRS, for example to ensure SRS deactivation when adeactivation request may be missed.

In an example, the WTRU may be configured with a duration parameter,e.g., D, for SRS transmission. The WTRU may receive an activationrequest, for example in a DCI or MAC-CE. The WTRU may transmit SRS untilthe WTRU successfully receives a deactivation request. The WTRU maytransmit SRS until a time (e.g., timer) expires where the time is basedon D. In examples, the WTRU may transmit SRS until it has made D (or afunction of D) SRS transmissions or sets of SRS transmissions, forexample since receipt of an activation. The WTRU may stop SRStransmission after D (or a function of D) SRS transmissions. Inexamples, the WTRU may stop SRS transmission after D time (or a functionof D time), for example since receipt of an activation. D may be in timeunits such as symbols, slots, mini-slots, subframes, frames, timebursts, time blocks, and the like.

The starting point from which to determine the time window or the numberof transmissions may be the time or time unit (e.g., subframe, slot,mini-slot, etc.) in which the SRS activation (e.g., the last or mostrecent SRS activation) is transmitted (e.g., by the gNB) and/or received(e.g., by the WTRU).

For example, a WTRU may receive an SRS activation in time unit (e.g.,subframe, slot, or mini-slot) n. A WTRU may begin transmitting SRS intime unit n+k. The SRS in time unit n+k may be considered the first SRStransmission for counting SRS transmissions. Time unit n or n+k may beconsidered the starting time (e.g., time 0) for counting time sincereceipt of activation.

The WTRU may restart its counting (e.g., of transmissions or time) whenthe WTRU receives an activation (e.g., re-activation) request before itstops SRS transmission that may have been initiated by a previousactivation request. A WTRU may ignore an activation (e.g.,re-activation) that it may receive before it stops SRS transmission thatmay have been initiated by a previous activation request, for example toavoid the possibility of continuing transmission due to amisinterpretation of deactivation as activation.

The duration parameter, which may be a maximum time window, may beconfigured by broadcast or WTRU specific signaling. For example, theparameter may be provided by RRC signaling. In examples, the parametermay be included in a MAC-CE such as the MAC-CE that provides theactivation and/or deactivation.

In an example, there may be a set of duration parameters and theconfiguration may indicate which of the duration parameters in the setto use. One of the duration parameters may indicate infinity or alwayswhich may, for example correspond to and/or result in the WTRU usingdeactivation, e.g., only a deactivation request, to stop SRStransmission after SRS transmission is activated.

In examples, deactivation may be indicated, e.g., in the MAC-CE or DCI,by a certain duration parameter (e.g., activation duration parameter)such as 0.

In an example, a WTRU may be activated (e.g., to transmit SRS) with aduration parameter such as infinity or always that may indicate to theWTRU to transmit SRS (e.g., according to a configuration that may havebeen previously received) until receipt of a deactivation. The WTRU maytransmit SRS in response to the activation. The WTRU may be activated ordeactivated with a duration parameter such as 0 that may indicate tostop transmitting SRS. The WTRU may stop transmitting SRS in response tothe activation or deactivation.

Demodulation Reference Signal (DM-RS) transmission may be provided. Forexample, DM-RS sequences may be mapped to interleaved subcarriers. TheDM-RS sequences associated with different antenna ports may bemultplixed by using orthogonal sequences (e.g., one for each antennaport) and/or spreading over adjacent OFDM symbols using time domainorthogonal cover codes (TD-OCC).

For example, one or more DM-RS configurations may be used, wherein aDM-RS configuration may be determined based on one or more of following:number of subcarriers used in an OFDM symbol or a DFT-s-OFDM symbol;orthogonal cover code (OCC) in time domain or frequency domain; numberof cyclic shift of a DM-RS sequence; and/or number of symbols (e.g.,OFDM symbols or DFT-s-OFDM symbols) used for DM-RS.

A number of subcarriers used in an OFDM symbol or a DFT-s-OFDM symbolmay be used to determine the DM-RS configuration. For example, a subsetof subcarriers within a PRB may be used and the subset of subcarriersmay be located uniformly within a PRB. For example, a PRB may have 12subcarriers in an OFDM symbol or a DFT-s-OFDM symbol; a firstconfiguration may use 6 subcarriers out of 12 subcarriers and may belocated every 2nd subcarrier (e.g., even-numbered subcarrier orodd-numbered subcarrier); a second configuration may use 4 subcarriersout of 12 subcarriers and may be located every 3rd subcarrier. A subsetof subcarriers within a PRB may be used and the subset of subcarriersmay be located non-uniformly within a PRB.

Orthogonal cover code (OCC) in time domain or frequency domain may beused to determine the DM-RS configuration. For example, OCC in timedomain (TD-OCC) may be used with two consecutive subcarriers in timedomain (e.g., a TD-OCC may use [1 1] and another TD-OCC may use [1 −1]);OCC in frequency domain (FD-OCC) may be used with two consecutivesubcarriers in frequency domain (e.g., a FD-OCC may use [1 1] andanother FD-OCC may use [1 −1]); a first configuration may use TD-OCC anda second configuration may use FD-OCC.

Number of cyclic shift of a DM-RS sequence may be used to determine theDM-RS configuration. For example, a first configuration may use N1cyclic shifts and a second configuration may use N2 cyclic shift.

Combinations may be used to determine the DM-RS configuration. Forexample, a first DM-RS configuration may use K1 (e.g., K1=6) subcarrierswithin a PRB, TD-OCC, and N1 (e.g., N1=4) cyclic shifts; a second DM-RSconfiguration may use K2 (e.g., K2=4) subcarriers within a PRB, TD-OCC,and N2 (e.g., N2=2) cyclic shifts; a third DM-RS configuration may useK1 (e.g., K1=6) subcarriers, FD-OCC, and N3 (e.g., N3=0) cyclic shifts,etc.

A DM-RS configuration of one or more DM-RS configurations may bedetermined based on one or more of following: subcarrier spacing (if asubcarrier spacing is below a threshold, a first DM-RS configuration maybe used (e.g., a DM-RS configuration uses TD-OCC); a second DM-RSconfiguration may be used (e.g., a DM-RS configuration uses FD-OCC) if asubcarrier spacing is above a threshold); carrier frequency; NR-PDCCHsearch space (or NR-PDCCH CORESET) (a first DM-RS configuration may beused if an associated DCI is received in a first NR-PDCCH search space(or a first NR-PDCCH CORESET) and a second DM-RS configuration may beused if an associated DCI is received in a second NR-PDCCH search space(or a second NR-PDCCH CORESET). NR-PDCCH CORESET may be referred to as aNR-PDCCH resource set); RNTI of a received DCI (one or more RNTIs may beused for an associated DCI and a DM-RS configuration may be determinedbased on the RNTI used for the DCI); MIMO mode of operation (a firstDM-RS configuration may be used when a WTRU is configured with a firstMIMO operation mode (e.g., SU-MIMO mode) and a second DM-RSconfiguration may be used when a WTRU is configured with a second MIMOoperation mode (e.g., MU-MIMO mode); the MIMO mode operation may bedetermined based on the associated DCI type); and/or mobility of a WTRU(e.g., WTRU speed).

Implicit DM-RS configuration determination for IFDMA based DM-RS may beprovided. FIG. 23 illustrates an example of port multiplexing usingIFDMA with orthogonal sequences and repetition. Two exampleconfigurations may be as follows.

For example, DM-RS sequence for an antenna port may be mapped to everyk-th subcarrier. As an example, in FIG. 23 , DM-RS sequences are mappedto every other subcarrier in an OFDM symbol. To multiplex multiple portson the same resources, up to K different sequences may be mapped on thesame subcarriers. The K sequences may be orthogonal. The same DM-RSsymbols may be repeated on the adjacent OFDM symbols. This may bedesignated Configuration 1 for ease of explanation.

For example, DM-RS sequence for an antenna port may be mapped to everyk-th subcarrier. As an example, in FIG. 23 , DM-RS sequences are mappedto every other subcarrier in an OFDM symbol. To multiplex multiple portson the same resources, up to M different sequences may be mapped on thesame subcarriers. The M sequences may be orthogonal. This may bedesignated Configuration 2 for ease of explanation. In this option,symbols from two different DM-RS sequences may be transmitted on thesame subcarrier over a number of adjacent OFDM symbols using orthogonalcover codes. For example (assuming 2 OFDM symbols), on subcarrier k,r1[1 1] and r2[1 −1] may be transmitted on the two OFDM symbols, e.g.,subcarrier k on the first OFDM symbol is loaded with r1+r2 and the samesubcarrier on the second OFDM symbols is loaded with r1−r2. In thisexample, r1 and r2 may be coefficients of DM-RS sequences.

If the channel on subcarrier k changes significantly from one OFDMsymbol to the other, loss of orthogonality may occur, and r1 and r2 maynot be separated perfectly at the receiver. This may be due to, forexample, phase noise as the phase noise may change from one OFDM symbolto the other. The impact of phase noise may be larger at higherfrequencies. Similarly, high mobility may cause loss of orthogonality.

A configuration for a DM-RS transmission may be determined implicitly byat one or more of the following. Configurations may be generalized suchthat one configuration (Configuration 1) may be a DM-RS configurationwithout time domain cover spreading while another configuration(Configuration 2) may be a DM-RS configuration with time domain covercodes applied over a number of adjacent OFDM symbols.

Carrier frequency (fc): If fc≥Fc, Configuration 1 may be used and iffc<Fc Configuration 2 may be used.

Subcarrier spacing (Δf): If Δf≥F, Configuration 1 may be used and ifΔf<F Configuration 2 may be used.

Speed (v): If v≥V, Configuration 1 may be used and if v<V Configuration2 may be used.

The parameters Fc, F, V may be configured by a gNB or a network.

Implicit DM-RS configuration determination for FDMA based DM-RS may beprovided. In a possible DM-RS configuration, the DM-RS ports may bemultiplexed over adjacent subcarriers using frequency domain orthogonalcover codes. Two example configurations with and without time domaincover codes may be as follows.

FIG. 24 illustrates an example of FDM of DM-RS symbols without timedomain cover codes. DM-RS ports may be multiplexed over adjacentsubcarriers using frequency domain orthogonal cover codes, for example[1 1] and [1 −1]. Adjacent OFDM symbols may be used to transmitdifferent DM-RS symbols of different DM-RS ports. For example, if theDM-RS symbols for 4 ports are a, b, c, d, then the transmitted symbolsare shown in FIG. 24 . This may be designated Configuration 1 for easeof explanation.

FIG. 25 illustrates an example of FDM of DM-RS symbols with time domaincover codes. DM-RS ports may be multiplexed over adjacent subcarriersusing frequency domain orthogonal cover codes. On top of this, timedomain cover codes may be used to spread the reference symbols overadjacent OFDM symbols. For example, if the DM-RS symbols for 4 ports area, b, c, d, then the transmitted symbols are shown in FIG. 25 . This maybe designated Configuration 2 for ease of explanation.

A configuration for DM-RS transmission may be determined implicitly byone or more of the following methods. These options may be generalizedsuch that one configuration (Configuration 1) may be a DM-RSconfiguration without time domain cover codes while anotherconfiguration (Configuration 2) may be a DM-RS configuration with timedomain cover codes applied over a number of adjacent OFDM symbols.Carrier frequency (fc): If fc≥Fc, Configuration 1 may be used and iffc<Fc Configuration 2 may be used. Subcarrier spacing (Δf): If Δf≥F,Configuration 1 may be used and if Δf<F Configuration 2 may be used.Speed (v): If v≥V, Configuration 1 may be used and if v<V Configuration2 may be used. The parameters Fc, F, V may be configured by a gNB or anetwork.

FIGS. 26 and 26A illustrate an example of PNRS frequency density forQPSK, 16QAM, and 64QAM modulation.

FIG. 27 illustrates an example of determining a frequency density for aPNRS transmission. A subset of PRBs for PNRS transmission may be basedon a WTRU ID (for example, to randomize multi-user interference). A PNRSfrequency density may be based on MCS level (e.g., a 16QAM may have adensity 1 and 64QAM may have a density 2).

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, WTRU, terminal, base station, RNC, or any host computer.

Although features and elements of the present specification may considerLTE, LTE-A, New Radio (NR), or 5G specific protocols, it is understoodthat the solutions described herein are not restricted to thesescenario(s) and may be applicable to other wireless systems as well.

What is claimed:
 1. A wireless transmit receive unit (WTRU), comprising:a memory; and a processor configured to: receive downlink controlinformation (DCI) that includes an indication of a set of downlinkresources and an indication of a modulation coding scheme, the set ofdownlink resources corresponding to a plurality of resource block (RBs)associated with a physical downlink shared channel (PDSCH) transmission;determine a phase noise reference signal density associated with thePDSCH transmission, wherein the phase noise reference signal density isdetermined based at least on the indicated modulation coding scheme; andreceive the PDSCH transmission via the set of downlink resources,wherein the set of downlink resources comprises a first subset of theset of downlink resources that is used for reception of one or morephase noise reference signals, the first subset of the set of uplinkresources is comprised in a subset of the plurality of RBs, and thesubset of the plurality of RBs that comprise the first subset of the setof uplink resources is determined based on at least a WTRU-ID.
 2. TheWTRU of claim 1, wherein the phase noise reference signal (PNRS) densityis a time density.
 3. The WTRU of claim 1, wherein, if the modulationcoding scheme is a first modulation coding scheme, the phase noisereference signal density is a first density, and if the modulationcoding scheme is a second modulation coding scheme, the phase noisereference signal density is a second density, and wherein the firstdensity is a higher density than the second density.
 4. A methodcomprising: receiving downlink control information (DCI) that includesan indication of a set of downlink resources and an indication of amodulation coding scheme, the set of downlink resources corresponding toa plurality of resource block (RBs) associated with a physical downlinkshared channel (PDSCH) transmission; determining a phase noise referencesignal density associated with the PDSCH transmission, wherein the phasenoise reference signal density is determined based at least on theindicated modulation coding scheme; and receiving the PDSCH transmissionvia the set of downlink resources, wherein the set of downlink resourcescomprises a first subset of the set of downlink resources that is usedfor reception of one or more phase noise reference signals, the firstsubset of the set of uplink resources is comprised in a subset of theplurality of RBs, and the subset of the plurality of RBs that comprisethe first subset of the set of uplink resources is determined based onat least a WTRU-ID.
 5. The method of claim 4, wherein the phase noisereference signal (PNRS) density is a time density.
 6. The method ofclaim 4, wherein, if the modulation coding scheme is a first modulationcoding scheme, the phase noise reference signal density is a firstdensity, and if the modulation coding scheme is a second modulationcoding scheme, the phase noise reference signal density is a seconddensity, and wherein the first density is a higher density than thesecond density.
 7. A wireless transmit receive unit (WTRU), comprising:a memory; and a processor configured to: receive an indication of a setof resources and an indication of a modulation coding scheme, the set ofresources corresponding to a plurality of resource block (RBs);determine a phase noise reference signal density, wherein the phasenoise reference signal density is determined based at least on theindicated modulation coding scheme; and determine a first subset of theset of resources, wherein the first subset of the set of resources areassociated with one or more phase noise reference signals, wherein thefirst subset of the set of resources is comprised in a subset of theplurality of RBs, and the subset of the plurality of RBs that comprisethe first subset of the set of resources is determined based on at leasta WTRU-ID.
 8. The WTRU of claim 7, wherein the phase noise referencesignal (PNRS) density is a time density.
 9. The WTRU of claim 7,wherein, if the modulation coding scheme is a first modulation codingscheme, the phase noise reference signal density is a first density, andif the modulation coding scheme is a second modulation coding scheme,the phase noise reference signal density is a second density, andwherein the first density is a higher density than the second density.10. The WTRU of claim 7, wherein the indication of the set of resourcesand the indication of the modulation coding scheme are received viadownlink control information.
 11. The WTRU of claim 10, wherein thefirst subset of the set of resources are associated with a physicaldownlink control channel (PDCCH) transmission.
 12. The WTRU of claim 7,wherein the indication of the set of resources and the indication of themodulation coding scheme are received via scheduling information, andwherein the processor is further configured to: determine a secondsubset of the set of resources, wherein the second subset of the set ofresources is used for transmission of data associated with an uplinktransmission; and send an uplink transmission using the first subset ofthe set of resources and the second subset of the set of resources. 13.The WTRU of claim 7, wherein the uplink transmission is a physicaluplink shared channel (PUSCH) transmission.
 14. The WTRU of claim 13,wherein the indicated modulation coding scheme is associated with thePUSCH transmission.